SummarySputum samples from control subjects with cardiac disease and from patients with asthma were assayed for albumin content and immunoglobulins IgA, IgG, IgM and IgE. The asthmatics were divided into three groups: one group had received disodium cromoglycate (DSCG) for at least 48 hr prior to sampling, another group was sampled daily after commencing DSCG therapy and the third group were not taking DSCG. Albumin and immunoglobulins accounted for approximately 8% of the total sputum proteins in each of the four groups of subjects. There was no significant difference in the mean sputum levels of albumin or the immunoglobulins, when expressed as a percentage of total sputum proteins, between the subjects in each group. However, the ratios of IgA/albumin and IgA/IgG in the asthmatic group receiving DSCG were significantly lower than the corresponding ratios in sputa from both asthmatics and control subjects with cardiac disease. The sputum IgE levels tended to be higher in the asthmatics than in the control group, but DSCG therapy had little effect upon sputum IgE levels.